<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>标识符</title>
    <script type="text/javascript">
        var a01_$=5;
        //标识符由字母、_、数字、$组成，数字不能开头
        var 7a01_$ = 3;
    </script>
</head>
<body>

</body>
</html>